The present invention relates to a dust-proof swinging switch device which preferably works as a window regulator switch of an automobile.
A power window system of an automobile according to the related art includes a plurality of window regulator switches provided at the door on the side of the driver's seat. Window regulator switches of this type constitute a so-called swinging switch device having a switching mechanism, the switching mechanism comprising an operation knob which is supported through a regulating mechanism such that it can swing from side to side and which is always returned to and held at a standby position and a circuit board on which a movable piece contacts and leaves a fixed contact according to the swing of the operation knob (see Patent Document 1).
FIG. 3 is a sectional view of an example of a switch device of this type showing a schematic configuration of major parts thereof. A switch body 1 has fixed contacts 2 and 3 which are laterally provided and which constitute a switching mechanism A and a movable piece 4 which is provided above the contacts and which contacts and leaves the fixed contacts 2 and 3. The switch body further has a pivotal support portion which swingably supports the movable piece 4 and which also serves as a common contact 5.
A switch cover 6 is attached to the switch body 1 so as to cover the same from above. The cover 6 is formed with an opening 6a in a part of the same located above the switching mechanism A, and an operation knob 7 is mounted such that it is partially exposed at the opening 6a. The operation knob 7 is in the form of a rectangular container which is open on the bottom side thereof. The knob has a hollow cylindrical portion 7a provided so as to downwardly project from the bottom side to a position inside the switch body 1. The operation knob 7 is pivotally supported on both sides thereof so as to be swingable by a shaft 8 which is provided at the switch body 1.
A pusher 10 is provided in the hollow of the cylindrical portion 7a, the pusher is urged outward (downward) by a compression coil spring 9 into elastic contact with a top surface of the movable piece 4. The movable piece 4 is formed with a cam-like surface which is recessed in the middle thereof and curved to have peaks on both sides of the recessed portion. Thus, the switching mechanism A is configured, in which the pusher 10 rotates from side to side (so-called swinging) in elastic contact with the movable piece 4 to urge the movable piece into and out of contact with the fixed contacts 2 and 3 and in which the pusher is normally automatically returned to a standby position at the recessed portion and held in that position. The movable piece 4 having the cam-like surface also serves as a regulating mechanism B in which the pusher 10 is slid by the compression coil spring 9 in elastic contact with the contact piece such that the operation knob 7 is normally held in the standby position in the middle thereof and in which the operation knob can swing from side to side at a predetermined angle.
An arcuate finger engaging portion 7b is formed on a side (the left side in FIG. 3) of the operation knob 7 to allow operations of the same. A recess 6b that is a continuation of the arcuate feature is formed at the edge of the opening 6a of the switch cover 6 associated with the finger engaging section 7b to prevent any interference to finger engagement, which provides high operability. The cylindrical portion 7a of the operation knob 7 is surrounded by a cylindrical wall 1a which projects upward from the switch body 1, and the open end of the wall is located in a high position inside the operation knob 7, which effectively prevents water and foreign substances from entering.
Patent Document 1: JP-A-2001-297648 (see FIGS. 2 and 4)
In the swinging switch device having the above-described configuration, dust and fine sand can enter a gap S between the switch cover 6 and the operation knob 7 at the opening 6a of the cover, and they can enter the switch body 1 from the opening at the top of the cylindrical wall 1a as indicated by the arrow D in a broken line. Especially, in the case of a window regulator switch of an automobile, dust and fine sand are likely to enter when the window or door is opened and closed and are likely to accumulate in the recess 6b formed on the cover 6. Under changes in air pressure and shocks attributable to reactions to the opening and closing of the door, the dust and fine sand can be dropped inward from the recess and then blown up to enter the switch body 1.
When the fine sand which has thus entered reaches the internal switching mechanism A and is deposited on the movable piece 4, the feel of operation of the same in combination with the pusher 10 in sliding contact therewith becomes bad. When the slide of the pusher 10 becomes worse, the swing of the operation knob 7 to the standby position may fail. Obviously, the fine sand can cause conduction failures when it is deposited on the fixed contacts 2 and 3. There is concern about the above-described problem even when only a small amount of fine sand enters because the sand is accumulated without being discharged and is blown up by shocks causes by the opening and closing of the door, which makes the environment undesirable for the switch which must operate with stability for a long period.